This invention relates to a focus actuator driving apparatus for driving an actuator which moves an objective lens in a focus direction in an optical disk apparatus, such as a compact disk player or optical video disk player.
In an optical disk apparatus, it is necessary to lock in a focus servo loop before recording or playing back information. Therefore, when a commencement of the focus servo is initiated, a focus search is executed first. In the focus search mode, the actuator is driven with a driving signal whose level periodically changes between two specific levels. The objective lens results in repeating a movement of coming close to and going away from a disk. When the objective lens is located near a focus position where a laser beam for recording or playing back information is focused on a disk, the actuator is switched, being driven by a focus error signal instead of the driving signal, thus lacking in the focus servo loop.
In a conventional apparatus, however, because no current is supplied to the actuator at the moment of switching, the focus servo loop can not be locked in surely by a disturbance.